We have been getting spurts of very heavy rain here too. It doesn't seem that much hotter and we have actually had cool nights but maybe it is that difference that is causing the thunder showers.
One of the hardest hit is a client that is a golf course. We had 9 inches of rain over 2 days in the period of about 1 hour each and they had to close half the course. Happened again yesterday while I was there and the lightning strikes are happening more often too.